This study is designed to: 1) Study the chemical nature of the SAA protein in the aged population. The protein will be isolated from serum and attempts will be made to detect differences in proteins isolated from different individuals. 2) Define the cell responsible for the production of SAA using immunofluorescence or peroxidase conjugated antibody and in vitro tissue cultures. 3) Study the effect of colchicine and thymosin in vivo and in vitro. These drugs have been shown to inhibit experimental amyloid deposits. The possibility that they act by decreasing synthesis, secretion or inhibit polymerization (in the case of colchicine) will be investigated by in vivo and in vitro studies. 4) Study the role of proteolytic enzymes in the pathogenesis of AA-related amyloidosis. BIBLIOGRAPHIC REFERENCES: Rosenthal, C.J. and Franklin, E.C.: Serum amyloid A (SAA) protein: Interaction with itself and serum albumin. J. Clin. Invest. 1977, in press. Gorevic, P.D., Greenwald, M., Frangione, B., Pras, M. and Franklin, E.C.: The amino acid sequence of duck amyloid A (AA) protein. J. Immunol. l977, in press.